Contemporary radio frequency (RF) communication systems typically allocate communication resources (channels or time slots) among several subscriber units. Generally, each subscriber desiring access to the communication system must transmit a call request code and receive a grant code before communication (transmissions) between two or more subscriber units may commence.
Since the communication resources of RF communication systems are limited, it is known to limit the duration of any single communication to a predetermined time interval. Should the subscribers participating in a call attempt to communicate beyond this time interval, a warning tone precedes automatic preemption of the communication, and the communication resource is reassigned to other subscribers. While designed to improve the capacity of a communication system, this practice tends to confuse and frustrate subscribers as calls are abruptly terminated. Moreover, such a ruthless call preemption scheme impedes effective communication, and may actually reduce the efficiency of the communication system, since, in practice, subscribers tend to immediately re-request access to the communication system to complete their call. This causes an increase in signalling traffic that may reduce the efficiency of the communication system below that of merely allowing the subscribers to complete the original call. Accordingly, a need exists for a method of encouraging subscribers to quickly conclude their communications, without hampering the capacity and efficiency of the communication system.